Default registry: add Skoppe's, remove Herokuapp

Merge pull request #1887 from dlang/add_codemirror ...

Add codemirror.dlang.org as the primary fallback registry.

Add codemirror.dlang.org as the primary fallback registry.

Clean up PackageManager handling of search path ...

The PackageManager is a complicated beast:
it is responsible for handling the local caches where downloaded
packages are stored, including looking up a specific version of a specific package.

One feature that stood out while going over the code was the ability to disable
the default search path.
After looking up inside of Dub more, it turns out that this feature is exclusively
used when dub is called with the '--bare' option.

However, when this happen, a special constructor of the Dub class is called,
one that calls the 'PackageManager' constructor with 3 dummy arguments,
and rely on a boolean being set to avoid those 3 dummy arguments having any effect.
This ends up with effectively providing the ability to toggle the ability to
search default search paths in theory, but in practice the dummy arguments
means that it wouldn't work, nor is it actually needed.

Instead, a special argument for the single-search path approach is provided now.
In order not to break library users, the public symbols have been deprecated,
but their usage still works.
Note that some symbols are deeply entangled: for example, 'Dub.m_overrideSearchPath'
being non-empty means that 'PackageManager.m_disableDefaultSearchPaths' is 'true'.
It also means that 'PackageManager.m_repositories' is unused (and can be empty).
Hopefully removing the ability to toggle the default search path will allow
us to simplify things and make 'PackageManager.m_repositories' the only way
to specify whether or not the default packages search path are used.

Note that additionally to the changes aiming to deprecate 'Dub.m_overrideSearchPath'
and 'PackageManager.m_disableDefaultSearchPath', an unused constructor of PackageManager
has been deprecated.

Merge pull request #1838 from Geod24/cleanup ...

Windows: Remove Roaming repository migration
merged-on-behalf-of: Nicholas Wilson <thewilsonator@users.noreply.github.com>

Remove traces of VibeCustomMain ...

VibeCustomMain support was removed in Vibe.d v0.7.0,
released over 4 years ago (2015-11-04).

Windows: Remove Roaming repository migration ...

This feature has been implemented in Dub v1.8.0, almost 2 years ago.

Fix local cache

Replace calls to NativePath.toString() with .name ...

This has been deprecated in vibe-core and only triggers with 'library-nonet'.

Remove version branches for no-longer-supported compilers

Turn some enums into [static] immutable

Remove unused branch

Revert "support dependencies as git url with exact commit"

Merge pull request #1765 from belka-ew/pr_vesion_commit2 ...

support dependencies as git url with exact commit
merged-on-behalf-of: Nicholas Wilson <thewilsonator@users.noreply.github.com>

Command dub lint added

Support dependencies as git url with exact commit

Merge pull request #1755 from kinke/ldc ...

Improve user experience with ldc2, incl. cross-compilation
merged-on-behalf-of: Nicholas Wilson <thewilsonator@users.noreply.github.com>

Improve cross-compilation support (replace `version` checks by BuildPlatform runtime checks) ...

Also fixes #1249. For LDC as implicit cross compiler, the file
extensions for libraries and object files etc. don't depend on the
compiler, but solely on the target. Targets selected with `--arch` are
correctly probed by dub, so that the parsed `BuildPlatform` represents
the target platform.

Support fetch sub-package

Project settings file

`alias Nullable.get this` will soon be deprecated. Use `.get`.

Support of init-exec sub package

Custom init type (#1658)

Merge remote-tracking branch 'upstream/stable' into merge_stable

also remove dead code-mirror2.dlang.io fallback

fix Issue #1522 - avoid insecure fallbacks ...

- opens dub for possible MITM attacks

improve package supplier fallback logic ...

- scope (failure) did swallow fatal errors
- improve logging of failures and successes
- rethrow failure of default registry instead of from the last one
- remove failing package suppliers, so we don't keep beating dead horses

Note that some retry logic is already done interally by package suppliers,
so a failing one is unlikely to recover on the next usage.

Merge pull request #1616 from andre2007/fix_issue_1401 ...

Filesystem package supplier updated
merged-on-behalf-of: Nicholas Wilson <thewilsonator@users.noreply.github.com>

Filesystem package supplier updated

Merge pull request #1589 from MartinNowak/filter_version_identifiers ...

Add experimental feature to improve build cache efficiency